As an ex military satellite communications engineer I certainly remember working with spread spectrum modulation and also frequency hopping technology in the 1980's. Wireless Local Area Networking technology today exploits a technology which was thitherto mostly hidden inside this shadowy domain of military communications and radar. This technology comprises a collection of ideas which are termed Spread Spectrum Techniques (SST). Spread Spectrum techniques have some powerful properties which make them an excellent candidate for networking applications. To better understand why, we will take a closer look at this fascinating area, and its implications for networking.

If you want to know how to fix your Wi-Fi, first you need to understand how it works

Before you set about fixing your Wi-Fi, it helps to know how the technology works.

That way, you can make an informed decision about the equipment you need to solve your issues, or whether a change of settings might help.

It’s a complicated subject, and we won’t attempt to cover everything (such as packet data, TCP/IP, or the ins and outs of wireless security), but by the end of this section, you should have a firm grasp of Wi-Fi’s fundamentals.

Signals and spectrum

Wi-Fi’s core premise is pretty simple – routers and adapters send and receive data using radio waves. It’s the same basic technology that’s used by radio and TV to receive terrestrial signals, mobile phones to make and receive calls, as well as video senders, baby monitors, and all sorts of other wireless devices.

In effect, all a wireless router or adapter does is translate the data it receives into a radio signal, which is decoded back into data at the other end.

Specifically, wireless routers use frequencies of 2.4GHz (or the range 2.412GHz-2.484GHz to be more precise) and, in the case of more expensive dual-band routers, 5GHz (4.195GHz-5.825GHz) to send and receive information.

But there’s far more to it than simply slinging streams of data to and fro. Each of these bands is further divided into channels, of which your router can use one or two simultaneously (when two are used simultaneously, it’s called channel bonding – see below for more details). In the 2.4GHz band there are up to 14 channels available, and up to 42 in the 5GHz band.

The idea is that by using different channels, neighbouring networks avoid stepping on each other’s toes. In an ideal world, for maximum performance and stable operation, your router should be running on a channel that no other network in range is using.

In reality, the true number of available channels is lower than these theoretical maximums, depending on where you live and which router you’re using.

In the UK and Europe, you’re legally allowed to use only channels 1 to 13 in the 2.4GHz space, and you’re restricted to 18 of the 42 in the 5GHz space. A Netgear router we use in our office, meanwhile, makes only four channels in the 5GHz space available for use.

This is compounded by the fact that when your router transmits on each channel, the effective width of its signal is about 20MHz, which, in the 2.4GHz space, means it can overlap up to eight neighbouring channels.

It doesn’t take a genius to work out that when more than three wireless networks are in close proximity to one another, co-channel and adjacent channel interference can become a problem.

Channel bonding (the ability some routers have to group two channels together, doubling the potential throughput) makes the congestion even worse – with several 40MHz wide channels hogging such a narrow spectrum, it’s like trying to squeeze several 21-stone men into a small lift.

Why 5GHz?

There is a solution to hand, however – 5GHz wireless. The advantages it holds over 2.4GHz are threefold. First, it’s far less congested. Fewer people own dual-band 5GHz routers and devices, so the chances are you’ll be able to set up your network on a completely congestion-free channel, which you perhaps wouldn’t over 2.4GHz.

Second, since the channels are further apart than in the 2.4GHz band (with 20MHz between each, compared with 4MHz or 5MHz) there’s much less opportunity for adjacent channel overlap. Even in the unlikely event that many 5GHz routers and devices are in close proximity to each other, maintaining a steady signal should be much easier.

Finally, and potentially the biggest bonus of all, there are relatively few non-networking devices currently using the 5GHz space.

Where users of 2.4GHz must contend with all manner of domestic interlopers, from microwaves to cordless phones, 5GHz networks are comparatively clutter-free.

Physical barriers

It isn’t all rosy in the 5GHz garden, though. Since the signal is of a higher frequency than 2.4GHz, it deals less well with walls, windows and floors, and this hits its ability to transmit and receive speedily at long range.

In Rustyice tests, we’ve routinely seen routers perform well over 2.4GHz, flawlessly transferring files wirelessly at a distance of about 40m, with two walls in the way.

When tested in the same location over 5GHz, most suffer a significant drop in transfer speed and weaker signal reception. Some fail to maintain a solid connection entirely. That means the more objects blocking your signal path, the worse the reception in the 5GHz band gets. It isn’t only building materials that get in the way – everything from humans to heavy rain can attenuate a wireless signal.

Choosing a 5GHz router

Restricted range isn’t the only problem afflicting 5GHz routers. Many devices, such as smartphones, internet radios and games consoles, don’t send or receive signals in that band.

It’s really only laptops and PCs with premium wireless cards that will take advantage of the 5GHz band.

That’s why high-end routers typically offer the choice of 2.4GHz and 5GHz bands, but you should take care when choosing a dual-band router.

Some routers can transmit on both bands simultaneously, while others require you to manually flick between the two. Needless to say, the former is the better choice.